Metal finish



Patented Aug. 21, 1934 UNITED. STATES METAL FINISH Harrison M. Batten, Highland Park, and Carl J.

Welcome, Lansing, Mich., assignors to The City Auto. Stamping company Toledo, Ohio, a corporation of Ohio No Drawing. Application October 19, 1931 Serial No. 569,853

16 Claims. (Cl. 20413) The invention relates to electrodeposited coatings upon a base metal either polished or unpolished. The process of electrodeposition herein described 'forms part of the subject matter of our co-pending application, Serial No. 685,146,

filed August 14, 1933.

An object of the invention is to produce an electrodeposit which can be built up to a con: siderable thickness without blistering or becoming roughened.

Another object of the invention is to produce'a coating adapted to be easily buiied to a high 'polish.

Another object is to obtain a metal or composition that may be electrodeposited over itself in successive layers.

Another object is to obtain a coating that is not only highly resistant to corrosion in itself but has that property of being electrodeposited to or buiied to a dense surface that closes up porosity within the electrodeposited coating.

A further object is to produce a coating adapted for use as an intermediate between a relatively rough polished or unpolished base metal and a r highly lustrous finish metal such as chromium.

These and other objects are obtained in the electrodeposited coating hereinafter more fully described. Our improved electrodeposited coating comprises a mixture or alloy of the two metals copper and tin.- The coating is obtained by a process which comprises the'electrolyzing of a cyanide solution containing both copper and tin using anodes containing both copper and tin. The composition of the bath may vary widely under different conditions depending-on the requirements of the particular work under treatment but in general it is desirable to maintain the proportions within the following limits:

Copper cyanide 011(0103. 5 to 35 grams per liter.- Sodium stannate NmSnO 5 to 35 grams per liter. Sodium cyanide (free)- NaOn 10 to 40 grams per liter. Sodium hydroxlde. NaOH 5 to 30 grams per l1ter.

' In the above table, 'it is to be understood that the main desirable ingredients are the copper cyanide, soluble stannate, soluble free cyanide, and a suitable alkali. Equivalent reagents for obtaining a solution containing such ingredients may also be used such for example as the potassium salts instead of the sodium salts and other equivalent substitutes.

As an example of a specific formula for the plated over the alloy formed by our process.

bath, the following preferred composition may be used:

The above solution gives good electrodeposits at current densities from 10 to 80 amperes per square foot and it is possible to carry the current density much higher. Adensity of 320 amperes per square foot has been used but this results in an abnormally high evolution of hydrogen and requiressome means for inhibiting the hydrogen at the cathode in order to obtain commercial satisfaction. v

The recommended temperature of operation of the bath is between 50 and 60 C. but satisfactory electroplating can be obtained at room temperatures although with less current efliciency. The anodes used are preferably of pure copper and pure tin alternately arranged but anodes of a mixture or alloy of copper and tin may be used in lieu thereof. The anodes show good corrosion in the bath, thereby maintaining the preferred composition of the electrolyte. It is a noteworthy fact that the copper anode is maintained very bright in the bath in contradistinction to the dull appearance due to oxide formation in other electroplating processes involving the use of copper anodes.

The operation of our bath at different current densities results in an electrodeposit of varying composition, the general rule being that at the lower current densities, there is a greater percentage of tin in the coating than at the higher current densities. With the preferred bath composition given above, we have. obtained deposits containing 80% copper and 20% tin at 20 amperes per square foot and deposits containing 87% copper and 13% tin at 80 amperes per square foot. These properties may be varied however "by changing the composition of the electrolyte.

Our process may be used for electroplating directly on iron and its alloys including steel. It may also be used for plating onother metals whether they bethe base metal or onlya coating over another base metal. Examples of such metals are copper, nickel, tin, zinc, cobalt, silver, as well as combinations of these metals such as nickel and cobalt, copper and zinc, zinc and aluminum, cadmium and v silver and copper and nickel. The above metals can also be electrortCiiur new composition hasthe following prope es:

(a) A high spreading property.

(b) Easy bufling.

(c) A minimum loss of metal upon bufling.

((1) High corrosion resistance.

(e) An improved surface for superimposing another coating. I

(I) Allows other metals to. be electroplated thereon in a smooth lustrous condition- (a) Does not peel even in thick deposits.

(it) Can besuperimposed over itself.

The process for obtaining our alloy as herein before set forth has the following advantageous properties: 4 r

1. High rate of deposition.

2. A greatly improved ability to be electrodeposited to a greater thickness without becoming either blistered or rough.

3. Ease of control. I

4. A greater ability to produce a suitable coating over wide ranges of solution composition.

5. A greater ability to produce,a suitable coating over wide ranges of current density.

6. A greater ability to produce a suitable coating from a hot or cold bath. 7. Moredeposit per unit of power input.

\ 8. The ability 'to control the composition of plated coating by varying the following factors, voltage, temperature, composition of solution and kind and distribution of suitable anodes.

Ihe electroplated coating may advantageously be used as an undercoat in the production of bright metal finishes. For example in chromium plating an automobile radiator .shell in order to obtain both resistance to corrosion and high luster, it iscommon practice to take the steel shell as it comes from the dies and subject it to a series of polishingoperations to remove die marks, cuts, slight metal distortions, pits and othersurface defects in the metal as otherwise these blemishes would show in the final finish. With our process, we are enabled to eliminate the mechanical polishing of the base metal and electrodeposit our metal or alloy directly on the unpolished metal. We place a suificiently thick coating of alloy so that it can be buffed without cutting through and because of the high spreading power of the alloy, the surface defects are completely-oblit erated leaving a highly buifed smooth surface for the final finish. Any type of finishmay then be superposed on the bronze. 'For example, bright chromium may be directly superposed or a nickel layer may be deposited, then buffed and finally covered with chromium. Our process eliminates the original polishing of the base metal and "also makes the finish more resistant to corrosion be cause the exceptional spreading. power of our metal causes the metal to be less porous." It is understood, however; that this improved process" may be also advantageously applied to metal surthe novel resultshereinbefore set What we claim as our invention is:

1."Electrodeposited metal containing IO-25% tin and the balance substantially copper.

2. Electrodeposited metal containing approximately.85% copper and 15% tin.

3. A composite article comprising a base metal having surface irregularities therein, an electroplated coating composed of copper and tin bond.-

ed to said metal and having a smooth, buffed surface free from corresponding. surface irregularities and an overcoating of another metal.

4. A composite article comprising a base metal having surface irregularities therein, an electroplated coating composed of Ill-25% tin and balance copper bonded to .said metal and having a smooth, bufled surface free from corresponding surface irregularities and an overcoating of an other metal.

5. A composite article comprising a base metal having surface irregularities therein, an electroplated coating bonded to said metal and having a smooth, buffed surface free from corresponding surface irregularities, said coating comprising a preponderance of copper and a substantial amount of tin and characterized by a substan tially higher spreading power than electroplated copper,'and an outer coating of bright metal.

6. A composite article comprising a base metal having surface irregularities therein, an electroplated coating composed of copper and tin bonded to said metal and having a'smooth, bufied surface free from corresponding surface irregularities and an outer coating of chromium.

7 A composite article comprising a base metal having surface irregularities .therein, an electroplated coating composed of copper and-tin bonded to said metal and having a smooth, buffed surface free from corresponding surface irregularities, a superposed coating of nickel and an outer coating of chromium.

8. A composite article comprising a base metal rough polished, with 80 to 120 emery, an electroplated coating composed of copper or tin bonded vto said base metal and having a smooth bufled surface.

9. An article comprising a base metal, a superposed electroplated layer comprising copper and tin and an outer layer of a bright metal.-

10. An article comprising a base metal, a superposed electroplated layer comprising copper and tin and an outer coating of chromium.

11. An article comprising a base metal, a superposed electroplated layer comprising copper and tinand a superposed layer of nickel.

12. 'An article comprising a base metal, a su-' .perposed electroplated layer comprising copper and tin, a superposed layer of nickel, and a superposed layer of chromium.

13; An article comprising a superposed electroplated layer comprising copper and tin and an outer layer of a bright metal.

14; An article comprising a ferrous'metal, a contacting'electroplated layer comprising copper and tin and a contacting layer of bright metal.

15. An article comprising a ferrous metal and successive contacting electroplated layers of bronze and chromium, said bronze comprising I copper and tin.

16. An article comprising successive contacting layers of ferrous metal, electrodeposited bronze, nickel and chromium, said bronze comprising copper and tin.

. HARRISON M. BA'I'I'EN.

CARL J. WELCOME- 1 ferrous metal, a 

